Variable magnification lens system

ABSTRACT

A 6-component zoom lens for use between fixed conjugates at magnification ranging from 1:1.02 to 1:0.615. The two outermost components and one inner component are movable relative to the remaining components to vary the focal length of the lens as it is moved between conjugates to vary the image magnification. The inner movable component helps to maintain a flat field over the entire magnification range.

United States Patent 1 McCrobie et al.

[ VARIABLE MAGNIFICATION LENS SYSTEM [75] Inventors: George L. McCrobie, Upland;

Roscoe J. Donnel, Glendale, both of Calif.

[73] Assignee: Xerox Corp., Stamford, Conn.

[22] Filed: Sept. 4, 1973 [21] Appl. No.: 393,844

[52] US. Cl. 350/184 [51] Int. Cl. G02b 15/18 [58] Field of Search 350/184, 186

[56] References Cited UNITED STATES PATENTS 8/1972 Lynch et al 350/184 X Feb. 11, 1975 3,728,010 4/l973 Mikami 350/184 Primary Examiner-Paul A. Sacher Attorney, Agent, or FirmRobert 1. Bird [57] ABSTRACT A 6-component zoom lens for use between fixed conjugates at magnification ranging from 1:1.02 to 1:0.615. The two outermost components and one inner component are movable relative to the remaining components to vary the focal length of the lens as it is moved between conjugates to vary the image magnification. The inner movable component helps to maintain a flat field over the entire magnification range.

3 Claims, 1 Drawing Figure VARIABLE MAGNIFICATION LENS-SYSTEM BACKGROUND OF THE INVENTION- This invention relates to variable magnification or zoom lenses, and more particularly to such a lens for use between fixed conjugate planes, as for'example in a photocopying apparatus.

It is an object of this invention to provide a variable magnification lens for use between fixed conjugate planes in a magnification range of 1:102 to 1:0.615.

Another object'of this invention is to provide such a variable magnification lens in which the image field is kept substantially flat; throughout the magnification range.

DRAWINGS The drawing is an optical diagram ofa variable magnification lens according to the'present invention.

DESCRIPTION ment lII together forming a convex-concave doublet.

Single lens 8 is a convex-concave meniscus lens, also designated IV. Single lens 10 is a concave-convex me niscus lens, also designated V. Doublet 12 includes a double concave lens element VI and a double convex lens element VII, together forming a concave-convex doublet. Back single lens 14 is a concave-convex meniscus lens, also designated VIII.

The entire lens 2 is movable relative to conjugate planes l6 and 18. The front and back single lenses 4 and 14 and the inner doublet 12 are movable lenses relative to the remaining lenses in lens 2. Suitable mechanism is provided for effecting the desired movement but is not a part of this invention and is not shown.

An important feature of this invention is the movement of the inner doublet 12 in conjunction with the outer lenses 4 and 14. Without this feature, and with only the outer elements movable, it was found that image field curvature changed rapidly and image quality deteriorated at the lower magnifications, especially below 1:0.65. The movement of inner doublet l2 functions to keep the image field substantially flat through out the magnification range.

The parameters of the lens elements which make up a specific zoom lens 2 are as listed in the following table in which N is the refractive index at 5876A wavelength and V is the dispersion value or Abbe number. Radii (R), thicknesses (T), and spacings (S) are expressed in inches and a negative sign indicates lens radii on centers of curvature on the object side of the lens. 5; and S indicate respectively spacings from object and image planes to their next adjacent lenses.

LENS RADlUS (R) THICKNESS (T) SPACINGtS) REFRACI'IVE DlSPERSlON INDEX N VALUE v,,

1.02x--23.2059s LOOK-23.48476 sex-24.04742 84X--25.864l9 .77X--27.()l600 71x--2s.07003 .65X--29.l3382 -Z5. .48 R,=3.59o2s 1.02x--.10290 1.00x--.100s0 96X. 10450 .s4x--.1457o .77x-:.199s0 .7lX--.2649O .65X--.35040 .s15x-.41500 R, =15.71o92 11... T,=.68986 l.6l405 55.17

R,'= -15.o120s s ,=.21e79 R,=3.43s79 IV... T4=.58942 1.66755 4 L93 R,=5.s92o6 ontinued LENS RADIUS (R) THICKNESS (T) SPACING(S) RgFRACrIvE DISPERSION INDEX N,, VALUE v,

What is claimed is:

l. A variable magnification lens for use between fixed conjugates and including the following components in optical alignment:

a first positive convex-concave meniscus lens 1;

a second positive double convex lens element 11;

a third negative double concave lens element 111;

said second and third elements forming a doublet,

a fourth positive convex-concave meniscus lens IV;

a fifth positive concave-convex meniscus lens V;

a sixth negative double concave lens element V1;

a seventh positive double convex lens element Vll;

said sixth and seventh elements forming a doublet,

an eighth positive concave-convex meniscus lens said second and third elements and said fourth and fifth lenses being fixed relative to each other as a unit,

said first and eighth lenses and said sixth and seventh elements being movable relative to said unit,

the entire variable magnification lens being movable between fixed conjugates.

2. A variable magnification lens according to claim 1 in which said magnification varies in a range of from substantially 1:1.02 to 120.615.

fixed conjugates and including the following components in optical alignment;

a first convex-concave meniscus lens 1;

a second double convex lens element 11;

a third double concave lens element 111, said second and third elements forming a doublet,

a fourth convex-concave meniscus lens IV,

a fifth concave-convex meniscus lens V,

a sixth double concave lens element V1,

a seventh double convex lens element V11,

said sixth and seventh elements forming a doublet,

an eighth concave-convex meniscus lens V111,

said second and third elements and said fourth and fifth lenses being fixed relative to each other as a unit,

said first and eight lenses and said sixth and seventh elements being movable relative to said unit,

the entire variable magnification lens being movable between fixed conjugates,

the parameters of lens radii (R), thickness (T), spacings (S), refractive indices (N), and dispersion values (V) being in accordance with the following table wherein radii, thickness, and spacings are expressed in inches and wherein endmost spacings are those between an end lens and its corresponding conjugate plane:

LENS RAD1US(R) TH|CKNESS(T) SPAC1NG(S) REFRACTIVE DISPERSION INDEX N, VALUE V,,

l,02X--23.20598 l.00X-23.48476 

1. A variable magnification lens for use between fixed conjugates and including the following components in optical alignment: a first positive convex-concave meniscus lens I; a second positive double convex lens element II; a third negative double concave lens element III; said second and third elements forming a doublet, a fourth positive convex-concave meniscus lens IV; a fifth positive concave-convex meniscus lens V; a sixth negative double concave lens element VI; a seventh positive double convex lens element VII; said sixth and seventh elements forming a doublet, an eighth positive concave-convex meniscus lens VIII, said second and third elements and said fourth and fifth lenses being fixed relative to each other as a unit, said first and eighth lenses and said sixth and seventh elements being movable relative to said unit, the entire variable magnification lens being movable between fixed conjugates.
 2. A variable magnification lens according to claim 1 in which said magnification varies in a range of from substantially 1: 1.02 to 1:0.615.
 3. A variable magnification lens for use between fixed conjugates and including the following components in optical alignment; a first convex-concave meniscus lens I; a second double convex lens element II; a third double concave lens element III, said second and third elements forming a doublet, a fourth convex-concave meniscus lens IV, a fifth concave-convex meniscus lens V, a sixth double concave lens element VI, a seventh double convex lens element VII, said sixth and seventh elements forming a doublet, an Eighth concave-convex meniscus lens VIII, said second and third elements and said fourth and fifth lenses being fixed relative to each other as a unit, said first and eight lenses and said sixth and seventh elements being movable relative to said unit, the entire variable magnification lens being movable between fixed conjugates, the parameters of lens radii (R), thickness (T), spacings (S), refractive indices (N), and dispersion values (V) being in accordance with the following table wherein radii, thickness, and spacings are expressed in inches and wherein endmost spacings are those between an end lens and its corresponding conjugate plane: 